1. Field
One embodiment of the present invention relates to a substrate for a magnetic recording media having protrusions and recesses formed thereon, a magnetic recording media of substrate processing type and a magnetic recording apparatus having the magnetic recording media mounted thereto.
2. Description of the Related Art
In increasing the track density of a hard disc drive (HDD), interference between the adjacent tracks has come to be a problem to be solved. In particular, how to lower fringing caused by the fringe effect of a magnetic field from the write head is a serious technical problem to be solved. A discrete track type patterned media (DTR media) in which recording tracks are physically separated makes it possible to suppress a side erase phenomenon in recording and a side read phenomenon in reproducing so as to increase markedly the density in the cross-track direction and, thus, is expected to provide a magnetic recording media capable of high density recording.
The DTR media includes a magnetic film etching type and a substrate processing type. A large number of manufacturing steps are required for obtaining the DTR media of the magnetic film etching type, leading to a high manufacturing cost. Therefore, the substrate processing type DTR media, prepared by first producing a substrate having protrusions and recesses and then depositing a magnetic film by sputtering, is suitable to mass production of the DTR media.
In the substrate processing type DTR media, however, the magnetic film is also formed on the recesses, with the result that the signal-to-noise ratio (SNR) is lowered by magnetic signals from the recesses. Under the circumstances, it is considered effective to lower the magnetic characteristics of the magnetic film present on the recesses.
A method of manufacturing a patterned media is proposed in, for example, Japanese Patent Disclosure (Kokai) No. 2002-359138. It is disclosed in this prior art that the surface of a ferromagnetic layer is selectively covered with a mask so as to permit the surface of the ferromagnetic layer to be selectively exposed to a reactive gas containing a halogen element, thereby denaturing the exposed portions. Also, a method of manufacturing a patterned media by selectively oxidizing the masked surface of the media is disclosed in U.S. Pat. No. 6,168,845. Further, proposed in Japanese Patent Disclosure No. 5-205257 is a method that ions such as nitrogen ions or oxygen ions are introduced into those regions of the magnetic layer positioned between the recording tracks of the discrete track media so as to make the magnetic layer on those regions nonmagnetic. However, it is difficult to carry out these methods.
Also proposed is a patterned media prepared by forming a multilayered Co/Pt magnetic layer on a Si substrate having protrusions and recesses; see Phys. Rev. B 62, 12271-12281 (2000). The magnetic characteristics of the Co/Pt multilayered film are highly sensitive to the multilayered structure. Specifically, a clear multilayered structure can be obtained on the protrusions and the multilayered structure is disturbed on the recesses, making it possible to form patterns. However, the particular method cannot be applied to a granular type perpendicular magnetic film.